Work blasting method and machine



June 6, 1950 R. B. HUYETT 2,510,927

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WORK BLASTING METHOD AND MACHINE 35 I ,7M1 W R. B. HUYETT WORK BLASTING METHOD AND MACHINE June 6, 1950 Filed Nov. 15, 1946 10 Sheets-Sheet 1O A a 0 &

maaw-ax/arfm Patented June 6, 1950 WORK BLASTING METHOD AND MACHINE Robert B. Huyett, Hagerstown, Md., assllnor to Pangborn Corporation, Hagerstown, Md., a corporation of Maryland Application November 15, 1946, Serial No. 709,941

' Claims. (01. 51-44) This invention relates to methods and means for treating castings, forgings and like articles to clean or otherwise modify the surfaces thereof. It is particularly applicable to the blast treatment of such articles in conveyor type blasting machines, especially blasting machines of the monorail conveyor type.

The principal object of the invention as applied to a conveyor type of blast machine is to increase the productivity thereof without impairment of its eflectiveness.

The invention consists in an improved method and means by which the articles being blast treated are moved rapidly to a blasting zone, moved slowly through the blasting zone during treatment, and thereafter moved rapidly from the blasting zone to a succeeding blasting zone or point of delivery, the articles in the preferred embodiment being rotated at least during the treating operation.

One of the forms of blast cleaning machines of the monorail and cabinet type which has become conventional in recent years employs a monorail conveyor having standard trolley type work carriers with hooks spaced at intervals, and connected in series by a chain. Th work conveyor of such machine is usually disposed to travel in a loop. The trolleys attached to the chain are propelled by a driving device engaging the chain. The work pieces are suspended on the hooks and passed through the cabinet enclosure, in which the work is exposed to blast streams of treating particles, which are usually projected from blasting devices spaced on the cabinet wall by distances approximately equal to the trolley-hook spacing.

In this conventional machine the work is intermittently moved to advance it from one blast stream to the next, the work being stopped at the approximate center of each blast stream (or at one side of such center) for an interval and being revolved through rotation of a conventional swivel unit in the hook suspension.

This known arrangement for rotating th work at one fixed blast position is satisfactory for cleaning exterior surfaces of a cylinder of suitable dimensions, but is not so satisfactory for cleaning of irregular cubical objects having pockets, bosses and other irregular surfaces, such as cylinder blocks of automobile engines, for example. With such articles certain pockets and sides are never hit by the blast streams in machines in which the work is rotated at one fixed 2 ventional type of machine, fully effective blasting is unobtainable.

In another monorail type blasting cabinet which has become conventional in recent years the monorail is continuously driven at a constant slow speed. This produces good blasting of the surfaces and pockets, but at a terrific sacrifice in production, and with poor econom of abrasive position relative thereto. Thus with this conso and disproportionate power consumption and wear of the parts. For example, proper blast cleaning of an automobile engine block in such a machine requires that the work move through the blast stream at approximately 32 inches per minute. With this slow constant speed of work traverse, and the monorail suspension hooks spaced about 32" apart, the production rate of the machine is only 1 cylinder block per minute, or blocks per hour. The airless-blast wheels of this conventional machine throw abrasive at the rate of about 100,000 lbs. perhour. Thus such a machine requires that about 1,667 lbs. of abrasive be thrown for each block treated.

With the method and apparatus of the present invention even more effective blasting is obtainable than in this uniform drivedevice, yet the production rate is greatly increased, great economy is effected in the use of abrasive, and wear of parts is reduced, as compared therewith.

For example, by applying the present invention to the type of machine just discussed the productivity of the machine is easily more than tripled, while the amount of abrasive required to be thrown is easily reduced to about 500 lbs per block treated, or less.

While the invention is particularly adapted for the abrasive blasting of engine blocks and the like to clean the same, it is not limited thereto.

Hence the reference herein to the cleaning of castings and the like contemplates'other treatments which may be practiced with machines of thischaracter. And while the invention is herein disclosed as applied to a blast-cleaning machine, its broader aspects are not to be considered as limited thereto.

In the accompanying drawings illustrating a preferred embodiment of the invention,

Figs. 1-4 are north, west, south and east side elevations of a blast cleaning machine of the monorail cabinet type in which the invention is embodied.

Fig. 5, 6 and 7 are sectional plan views taken on the lines 5-5, 8-6 and 1-1 of Fig. 2.

Fig. 8 is a detail of the work hanger and tripping mechanism of this embodiment. 1

Fig. 9 is anend elevation of the hanger of Fig.

8. and Fig. 10 is an elevational detail taken on the line Il-IO of Fig. 8, looking in the direction of the arrows.

Fig. 11 is a diagram of the conveyor driving arrangement of the machine.

Fig. 12 is a diagram of a modifled driving arrangement.

Figs. 13, 14 and 15 are diagrams illustrating the method of this invention as applied to engine blocks, for example.

General assembly As is shown more or less diagrammatically in Figs. 1 to 7, a machine for practicing and embodyins the new method and apparatus of this invention preferably comprises a conveyor means for establishing a path of movement of the work, herein shown as a monorail conveyor driven by chain A. In accordance with the general practics of the art, this conveyor may be arranged to travel in a closed path as shown (see particularly Fig. and may be provided with a tightener A, which may be of the fluid pressure tensioned type. as best shown in Figs. 3 and 5. This conveyor may be of any suitable form and may comprise the flanged guide rail B (Figs. 1-4) shown as of I-beam section, from which may be suspended spaced work hangers or supports C, which are linked together by chain A, as diagrammatically indicated in F 88- 1-7 and more fully shown in Figs. 8-10, hereinafter described.

Associated with the conveyor A is a suitable treating chamber or housing D, shown as supported on I-beam members at the floor level. Thishousing,asisusualintheart,maybe provided with swinging doors, or labyrinth passageways, through which the work carried by the conveyor ABC may enter and leave the treating zone. In this manner the conveyor may move the work to, through and from the treating zone without egress of dust and the like from the treating chamber. The main treating or blasting zone E, within the housing D, is provided in its side wall with a plurality of devices F for projecting abrasive or other treating particles across the path of the work established by the conveyor ABC. In the form shown the projecting devices F are oi the centrifugal airless blast machine type, and are spaced along the work path by distances approximate y equal to the spacing of the work supports C. Any number of such projecting devices may be employed, four being shown in the illustrative embodiment. Each such device is preferably provided with its own driving motor and with suitable means for controlling the direction of discharge of its blast stream. Any suitable type of treating'device may be employed, thatshown in Patent No. ,352,588 to Rosenberger et al., dated June 27, 1944, being eminently satisfactory. As is more fully described'hereina'fter, the several treating devices F are arranged at diiferent elevations, and pro- Ject their blast streams at diiferent angles across the work path, sons to properly'treat any or all the work past manual or other special treatment zones, outside or inside of the housing .D, as the manual touch up. zone C and the nozzle -blasting zone H. for example, as is well known in'the art.

The spent treating particles and refuse, as is usual in the art.v may pass through perforated floors or gratings J underlying the several treating miles, into hoppers K, and be conducted therefrom by conveyor means, as the chutes L and elevator M, to a particle separator N. The separator N may comprise a rotary screen for removing coarse refuse from the particles, as shown, and may be provided with an air-wash means for removing flne dust from the cascading particles. The cleaned particles passing from the separator N in the form shown are collected in a particle storage hopper P from which they pass through valves Q (Fig. 4), controlled by solenoid R, to the feed spouts of the centrifugal projectors S, and through other lines T to the nozzles or other devices employed at zones 0 and H for example. A suitable replenishing bin U (best shown in Fig. 2) may be connected to introduce an additional quantity of treating particles to any part of the particle recirculating system, and a dust exhaust duct V may be connected to the housing D, as through the baiile chamber W, preferably at a point remote from the work entrance and exit openings. Suitable access doors are provided in the housing as is well known in the art.

Work handling means As is more particularly shown in Figs. 8 and 9, the conveyor work-supports or hangers C of this illustrative embodiment are suspended from the guide-rail B by wheels or rollers 20, rotatable in a U-shaped hanger plate 2| which in turn is secured to the load bar 22 of the hanger. The load bar 22 of each hanger C comprises two outer flanged plate members and an inner flat memher, as showmand is assembled in an aperture extending through a link-block 23 of the conveyor chain A, and is thus secured to the chain. The load bar 22 has secured to its lower end a hanger bracket assembly 24 which supports two spaced bearings 25. These bearings rotatably support the hanger shaft 28 which has at its lower end a work-coupling member 21* to which a hooked rod or other work-supporting flxture 21 may be detachably secured. The hanger shaft 26, intermediate the bearings 25 is provided with a whirl, shown as a sprocket 28, which projects from the open sides of the bracket assembly 24 and is adapted to be engaged by rotating means such as the work rotating chain Y, Fig. 9, hereinafter described.

The lower end of the work hanger assembly so far described, as is best shown in Fig. 9, extends through a slot in the roof of the housing D, and is provided with an appropriate seal. To this end the roof of the housing D, at either side of its slot, is provided with channel members 30 and the hanger assembly 24 extends between these channel members and is provided with guide rollers 3| running therebetween. The seal is eifected by the provision of flange plates 32 on the channel members 30 and by the provision of seal plates 33 secured to the hanger bracket assembly 24 and to which are pivoted further overlapping seal plates 34 to in effect constitute a second chain securing the hangers C against excessive sway g.

As is shown in Fig. 8, there is also associated with the conveyor chain A a tripper supporting means, generally indicated at X. This tripper supporting means in the form shown is suspended from the guide rail B by a wheel, hanger plate and load bar assembly generally similar to that of the hanger C and similarly secured to the chain A. This load bar not only carries the control tripper arm 11, hereinafter described, it also supportstheupperendofashaftlltowhichis secured a guide-roller and seal assembly like that carried at the lower end of the hanger bracket assembly 24. As the seal plates 35 and 34 are longer than the blocks 25 and the plates 23a. of chain A, the tripper support x and shaft 35 in the form shown are Joined in offset relation. A freely rotatable guide sprocket I8 is mounted on the shaft 35 and serves to help maintain the proper alignment of the work-rotating chain hereinafter described.

The control tripper. as is shown-in Figs. 8 and 10, comprises a projecting cam arm 51 which is carried by the tripper support X, and in the form shown is located at the head of the shaft 35. As is shown in Fig. 10, this cam arm 31 projects laterally of the path of travel of chain A in position to contact the arms or other actuating members of two limit switches 38 and 59, each of which is preferably mounted on a limit switch support, shown as an angle iron member 40 suitably supported above the roof of cabinet C. Provision is made for adjustment of the position of each limit switch lengthwise and crosswise with respect to the direction of travel of the conveyor chain A, as by providing the support 40 with a longitudinally extending slot, and each switch basewith transversely extending slots, to receive the switch securing bolts, as shown in Fig. 10.

, As is best shown in Figs. 2 and 6, a suitable work rotating chain Y is mounted on guide sprockets 41 carried by sprocket supports 42 which in the form shown are mounted on the cabinet top. This rotating chain Y, as above described, meshes with the sprockets 38 and 28 (Fig. 8) when the particular tripp r support X and work support C have entered the housing D and reached the position at which rotation of the work is to be initiated. As shown in Fig. 9, the chain Y may be of the well known triple type with its center section engaging the sprockets 36 and 28 and its marginal sections engaging the guide sprockets 4|. It may be provided with any suitable tightening device. For example, the guide sprockets 4|, nearest the driving motor 45 (Fig. 6) may be movably mounted and urged toward tensioning position.

Power driving elements Each of the moving elements above described is provided with suitable driving means. Preferably independent motors are employed, withspeed reducersin certain instances. Thus, motors with appropriate speed reducers are shown at 43 for driving the elevator M, at 44, for driving the revolving screen N, (Figs. 1, 2 and 4) and at 45 for thework rotating chain Y (Figs. 2, 3 and 6). In this illustrative embodiment of the invention two motor and reducer drives 48 (Figs. 2 and and 41 (Figs. 3 and 5) are provided for driving the conveyor A, to enable the new method of work handling to be carried out.

Work handling controls veyor ABC at a rapid rate during its approach tothebiaststreamanduntiiitsleadingedgeis located in the blasting stream. The controls are so arranged that motor 40 then takes over the driving of the conveyor ABC to move the article through the blast station at a predetermined slow rate until its trailing edge only is in the blast stream, after which the motor 41 takes over the drive of the conveyor ABC and moves the work rapidly from the vicinity of the blast stream, or until it reaches the vicinity of the next blast stream. The conveyor ABC is thus alternately driven at a slow rate while the articles are being treated in the blast streams, and at a rapid rate while they are being moved from one blast stream to the next, and the slow rate driving is preferably so related to the rate of rotation of the work by the rotating chain Y (Figs. 2 and 6). that the work is rotated through a predetermined integral number of revolutions during its period of slow traverse through the blast streams. In the preferred embodiment provision is also made for adjusting the speed of slow driving, or the speed of work rotation, or both, to more accurately control the blasting operation.

To this end, as shown in Fig. 11, the slow-driving motor 48, connected through a speed-varying device as the variable speed pulley 50, drives a speed reducer, as the worm and wheel reducer 51. The speed reducer 5| is connected as by chain drive 52, to the driving member of a one-way driving unit 53. This unit may take the form of a pawl and ratchet device, as diagrammatically indicated in Figs. 1-7 and 11, the pawl means of which effects the driving action. The ratchet, or driven member of this unit 53 is connected to the shaft 54 which carries the main driving sprocket 55 for the conveyor ABC. The fastdrive motor 41 does not'need to be provided with a speed varying device, though one may be employed, if desired. In the form shown the motor 41 is connected directly to the speed reducer 58, which is connected as by chain drive 58 to'the driving member or pawl means of a second oneway driving unit 60, likewise shown as of the pawl and ratchet type. The ratchet, or driven member, of this unit is likewise connected to the shaft 54 which drives conveyor ABC.

The conveyor ABC, as above noted, carries the tripper cams 31, which engage the limit switches 38 and 39 adjacent the path of movement of the tripper. When the main switch 61 and manual motor switches 82 and 63 in the main power supply lines to motors 46 and 41 are first closed, the relay switch 64 in the circuit ofthe motor 41 remains open. The conveyor ABC is therefore driven at slow speed by motor 46, through elements 50-55, the shaft 54 turning freely in the one-way drive unit 60.

When the work carried by one of the hangers C has passed through the first of the blast streams projected in the blasting zone by the projecting devices F (Figs. 4 and 6) one of the tripper cams 31 actuates the fast drive initiating switch 39, the relay switch 84 (Fig. 11) is closed and motor 41 is put into operation. The conveyor ABC is then driven at a relatively rapid rate by the motor 41, through elements 58-60, 54, 55 and chain A, the shaft 54 turning freely in the more slowly operating one-way drive unit 53.

When the next work piece reaches the first of the blasting streams (that previously treated reaching the second thereof) one of the tripper cams 31 actuates the slow drive initiating switch. 38. Operation of this switch causes opening 01 the relay switch 64. The fast driving motor 41 then stops (it may be provided with a brake, if desired, to prevent drifting), and the conveyor ABC is again driven at slow speed by motor I, until the fast drive initiating switch 39 is again actuated as the work is carried out of the blasting stream.

Any suitable form of control or pilot circuit may be employed for controlling operation of the slow and fast drives in timed. relation to the operation of the conveyors, and this circuit is therefore exemplified in a simplified manner in Fig. 11. As there shown, the pilot circuit includes the coil of a spring biased relay switch 64, the coil of a spring biased fast drive holding relay i5, and the two limit switches 38 and 39, which are shown as normally closed and normally open, respectively. The contacts of the fast drive holding relay G are connected in'parallel with the fast drive initiating switch 39.

When switch 39 is closed, current flows through the pilot circuit and the switches 39 and 39 in series. This current flow closes the motor relay switch 64 and at the same time energizes the fast drive holding relay 95. Thus when the tripper cam 31 releases switch 39 and it returns to its normally open position the pilot circuit remains closed through the switch 38 and the contacts of the holding relay 65. Thus when the next tripper cam 31 actuates the slow drive initiating switch 38 to open the same, the pilot circuit is opened and the relay switches 64 and 55, being no longer held closed by their coils, return to their spring biased open positions. If desired, manually controlled or other alternatively used slow and fast driven initiating switches may be placed in series and in parallel, respectively, with the switches 38 and 39, as indicated at I38 and I39.

. The work rotating chain Y may be arranged to travel in the same direction as the conveyor ABC, or in the opposite direction, and may engage the whirl sprockets 28 from either side. I prefer however to arrange the rotating chain as shown in Figs. 2 and 6, for economy of chain and space, and to rotate it in the same direction as the conveyor ABC. With this arrangement, as the conveyor ABC is speeded up, the speed of rotation of the work is reduced, and vice versa. Thus a part of the energy of the system is stored alternately as rotary and linear kinetic energy and some economy of power is realized.

Alternative work handling controls Another arrangement, employing only one reducer unit and but a single one-way driving.

' nected through a speed varying device, as the variable speed pulley 50a, to the driving member or worm shaft of the reducer H, through a one- I way driving means, as the over-riding clutch 53a. The main and manual motor switches la, 82a, 63a, and the relays 64a, 65a are substantially like those shown in Fig.,1l, and the fast drive initiating switches 39a and I 39a are likewise similarly arranged. Here, however, the slow drive initiating switches 33a and BM are normally open, and are arranged so that when either of them is closed it short circuits the coil of the fast drive holding relay "a. With this arrangement, closing of switch "a (or Illa) completes the pilot circuit through the-coils of relays a and "a, and closes their contacts. The pilot circuit thus remains closed through the contacts of relay in. when switch 39a (or l39a is released. Closing of switch 33a (or "811) simply short circuits the coil of relay 95a, allowing its contacts to open and break the pilot circuit.

With this arrangement, current is continuously supplied to the slow driving motor lie when the machine is in operation, and the reducer II is therefore driven at least at the speed selected by the variable speed device 500. The fast-drive motor "a being connected to the reducer shaft, is rotated idly thereby during the slow driving. When the fast drive motor "a is energized it drives the reducer H at an increased speed, the one way drive device, shown as an over riding clutch 53a, allowing the reducer to run away from the now idling slow-drive motor 46a. When the fast drive motor "a is deenergized, however, the over riding clutch picks up and the reducer is driven at the slow driving speed.

Blast-method achieved By handling the work in accordance with the method above described, highly efiective and uniform blast treatment may be accomplished with a greatly increased rate of production and with great overall economy. The quantity of abrasive or other treating medium projected per article treated is greatly reduced, effecting a saving of the portion thereof which is consumed and must be replaced. More work may be accomplished during the working life of the various parts of the machine, as it is wearing itself out to no purpose, during indexing of the work, for only the smallest practicable time since the fast drive indexing, to move the work from one blast stream to the next, is carried out at the maximum rate feasible. The relatively rigid linking of the work supports C to the seal-chain 33-34 as well as to the conveyor chain A and monorail, and the conducting of both of these chains about a loop or curve, at at least one point in their paths, aids in reducing swaying of the work supports at the moments of change from fast to slow driving, and vice versa, and enables a maximum rate of fast driving to be used. At the same time a highly effective blasting of the work is achieved, as indicated in Figs. 13 to 15 for example, which illustrate the blasting of a cylinder block by the method of this invention.

In the case of Figs. 13-15 the work pieces are assumed to be automobile cylinder blocks about 15 inches tall, 15 inches across the bottom, 11 inches across the top, and, say two to three feet long. These work pieces are suspended with their long axes vertical, from the rotatable work supports C, as shown in Fig. 15, and are then conveyed as shown in Fig. 14, with slow travel and relatively fast rotationthrough each of the several blast streams, and with fast travel, preferably accompanied by relatively slow rotation, from each blast stream to the next. The hangers C vand blast wheels S may be spaced about 32 inches apart, and the slow travel distances may be chosen at about 8".

of all ends, surfaces, and pockets of the work piece. The speed of rotation of the work and the 9 length of time of its exposure to each blast stream, are adjustable or-adjusted to eflect the desired degree and uniformity of blasting.

In Fig. 13 the upper line of the diagram represents a blasting operation with the work pieces rotated at the rate of one complete turn of the work during its slow travel through the blaststream, the total period of slow travel being 15 seconds, and the total movement of conveyor A in that time being 8 inches. The indexing (see Fig. 14) -may cover a distance of 2 feet in 3 seconds. a rate 15 times as fast as the slow drive.

'In the same figure; the lower line fully represents the first half of a blasting operation with the work pieces rotated at the rate of four complete turns during the totalinterval of slow travel, the other conditions being the same as in the upper line. The speed change'may be effected in any desired manner, and is readily effected by interposing, in the drive from motor", a variable speed pulley such as that shown at 50, Fig. 11, for example.

In each of these representations, the workpiece is shown as having a plane of general symmetry and as starting its slow travel with this plane parallel to the plane of the blast stream. The complete blasting operation may thus be visualized from the half thereof which-is completely shown, it being appreciated that the omitted portions of the diagrams of Fig. 13 are virtually mirror images of the parts illustrated in detail. If the work is to be considered as entering the blast stream with its plane of general symmetry in another position, say the third position shown in each of the two illustrations, the complete diagram therefor would be similar to that indicated, but would be shifted to begin and end with the work in that position.

.In certain cases, it will be desirable to predetermine exactly the orientation at which the work enters the blast stream, to insure that its position, with respect to the blast stream, will be such at a. given point in its passage therethrough as to effectively blast a particular pocket or area. Thus while the work does not have to enter any one, or all, of the blast streams in the same or any vparticular position of rotation, and the invention in its broad aspects, is not limited in this respect, it does contemplate, where this is desirable, that the respective parts of the driving apparatus may be so designed as to impart to the work a predetermined extent of rotation, as a given whole number of turns thereof, not only during each period of slow travel, but also duringeach period of fast travel, so as to present the work in the, same or other predetermined positions of rotation to each of the successive blast streams, and in certain cases considerable advantage may be attained by such practice.

In those cases in which overall uniformity of blasting is desired, the work should be so rotated as to expose all sides of it substantially equally to the blasting operation. The fewer the number of complete turns made during blasting, the more desirable it is that an integral number of turns be closely adhered to, since in this more economical case a larger part of the blast occurs in each revolution of the work, while in the case of a larger number of turns with only a small part of the total treatment occurring in each turn, a departure from an integral number of turns still results in substantially equal exposure of all sides of the article to the blasting operation.

As shown in the top line of Fig. 13, in which the work is illustrated as entering the blast stream in a particularly advantageous manner, the

10 stream first strikes the bottom edge of the block and then sweeps into the adjacent half of the crank recess thereof. It then sweeps the opposite outer side surfaces and half of the top surface of the block with a changing angle, as shown. Then. as,is apparent from the virtual mirror image of the diagram, the remainder of the top and outer surfaces are swept, followed by cleaning of the opposite half of the crank recess (notpreviously swept) and the adjacent bottom edge of the cast-' ing. By this method of procedure, each side of the casting receives almost identical treatment, the more remote surface recesses are blasted in planespractically'normal to their surfaces, and piston recesses are blasted from both ends by streams sweeping into them at changing angles.

Where it is desiredthat all outer surfaces of theblock receive particularly uniform treatments, the work may be rotated more rapidly, as shown in the lower line of Fig. 13. As there indicated, the operation is generally the same as before, but is repeated four times with the work. advanced into different relations to the blast stream. Thus each surface area receives more uniform proportions of blasting in planes nearly aligned with, and steeply inclined from, the normal to the blasted surfaces.

By blasting in accordance with this method, completely satisfactory treatment may be effected at the rate of 18 seconds per block, or 200 blocks per hour. With the projectors F throwing a total of 100,000 lbs. of abrasive per hour, this amounts to but 500 lbs. per block. Thus by the present method and apparatus a 333% increase in productionis achieved without sacrifice of efilciency of blast treatment as compared to uniform drive practice.

In addition the consumption of abrasive particles during non-useful projection thereof is reduced to less than '7 of that occurring in standard practice, and useless wear of the projectors and associated particle handling parts is correspondingly reduced, with a concurrent saving in power consumption, giving an overall increase in efliciency far in excess of 333 ,While the invention has been described with particular reference to the illustrations and embodiments shown in the drawings, it is to be understood that changes may be made in the method and apparatus without departing from the spirit and scope of this invention as set forth in the appended claims.

I claim: I

1. A method of blast-treating castings, forgings and like articles being translated along a path leading to, through and away from a blasting zone having a'blast stream directed across the path thereat, which consists in moving the article to be treated along said path at a, rapid rate until its leading edge is located in the blasting zone, then moving the said article slowly along said path until its trailing edge only is in said blasting zone, again moving said article along said path at a rapid rate to remove it from the blasting zone, and rotating the article at least during its interval of slow travel through the blasting zone.

2. A method of blast-treating castings, forgings and like articles being translated along a path leading to, through and away from a blasting zone having a blast stream directed across the path thereat, which consists in moving the article to be treated along said path at a rapid rate until its leading edge is located in the blasting zone, then moving the said article slowly along said path until its trailing edge only is in said 11 blasting zone, again moving said article along said path at a rapid rate to remove it from the blasting zone, and rotating the article through a predetermined number of whole revolutions during its interval of slow travel through the blasting zone.

3. A method of blast-treating castings, forgings, and like articles being translated along a path leading through a plurality of blast streams spaced longitudinally therealong and each directed thereacross, which consists in moving the article to be treated along said path at a rapid rate until its leading edge is located in the first of said blast streams, then moving the article slowly along said path until its trailing edge only is in said blast stream, again moving the article along said path at a rapid rate until the leading edge oi the article is located in a succeeding blast stream, again moving the article slowly along said path until its trailing edge only is in said blast stream, again moving the article along said path at a rapid rate to remove it from said last named blast stream, and rotating the article at least during its intervals of slow travel through said blast streams.

4. A method of blast-treating castings, forgings, and like articles being translated along a path leading through a plurality of blast streams spaced longitudinally therealong and each directed thereacross, which consists in moving the article to be treated along said path at a rapid rate while not in said blast streams and at a slow rate while being treated therein, and rotating the article at least during its exposure to said blast streams.

5. A method of blast-treating castings, forgings, and like articles being translated along a path leading through a plurality of blast streams spaced longitudinally therealong and each directed thereacross, which consists in moving the article to be treated along said path at a rapid rate while not in said blast streams and at a slow rate while being treated therein, and rotating the article through a predetermined whole number of revolutions during its exposure to said blast streams.

8. A method of blast-treating castings, forgings, and like articles being translated along a path leading through a plurality of blast streams spaced longitudinally therealong and each directed thereacross, which consists in moving a series oi articles to be treated along said .path in spaced relation corresponding tothespacing of said blast streams, eii'ecting said movement at a slow rate while articles are being treated in said blast streams and at a rapid rate in the intervals during which the articles are moving from one blast stream to the next, and rotating the articles at least during their exposure to said blast streams.

'I. A method of blast-treating castings, forgings, and like articles being translated along a path leading through a plurality of blast streams spaced longitudinally therealong and each directed thereacross, which consists in moving a series of articles to be treated along said path in spaced relation corresponding to the spacing of said blast streams, eflecting said movement at a slow rate while articles are being treated in said blast streams and at a rapid rate in the intervals during which the articles are movin from one blast stream to the next, and rotating 12 8. A method of blast-treating castings, forgings, and like articles being translated along a path leading through a plurality of blast streams spaced longitudinally therealong and each directed thereacross, which consists in moving a series of articles to be treated along said path in spaced relation corresponding to the spacing of said blast streams, effecting said movement at a slow rate while articles are being treated in said blast streams and at a rapid rate in the intervals during which the articles are moving from one blast stream to the next, and rotating the articles through a predetermined whole number of revolutions during their exposure to each of said blast streams.

9. A method of blast-treating castings, forgings and like articles being translated along a path leading through a plurality of blast streams spaced longitudinally therealong and projecting thereacross from diil'erent elevations, which comprises moving a, series of articles to be treated along said path in spaced relation corresponding to the spacing of said blast streams, effecting said movement at a slow rate while the articles are being treated in said blast streams and at a rapid rate in the intervals during which the articles are moving from one blast stream to the next, and rotating the articles through a predetermined whole number of revolutions during their exposure to each of said blast streams.

10. A method of treating castings, forgings and like articles being translated along a path leading to, through and away from a treating zone at which a treating medium is projected against'the articles, which consists in moving the article to be treated along said path at a, relatively rapid rate and rotating it relatively slowly as it approaches said zone, moving the article along said path at a relatively slow rate and rotating it at a relatively fast rate while it is passing through said zone, and again moving the article along said.

path at a relatively rapid rate and rotating it at a relatively slow rate as it leaves said zone.

11. A method of handling castings, iorgings and like articles being translated along a path leading to, through and from a blasting or like treating zone, which consists in moving the article to be treated along said path at a relatively rapid rate as it approaches the treating zone, moving the article being treatedv along said path at a relatively slow rate and concurrently rotating it as it passes through said treating zone, and moving the article along said path at a relatively rapid rate as it leaves said treating zone. i

12. Apparatus for blast treating castings, forgings and like articles, comprising means for establishing a stream of treating particles traveling at blasting velocities, conveyor means adapted to advance articles sequentially and in spaced relation through said stream to be treated thereby, and difierential driving means arranged to drive said conveyor at a slow rate of speed through those portions of its travel in which the articles are being treated in said stream and at a relatively high rate of speed during the remaining portions of its travel.

13. Apparatus for blast treating castings, forg lugs and like articles comprising means for establishing a stream of treating particles traveling 13 drive said conveyor at a slow rate of speed during those parts of its travel in which the rotating articles are being treated in said stream, and at a relatively high rate of speed during the remaining portions of its travel.

14. Apparatus for blast treating castings, forglngs, and like articles comprising means for establishing a stream of treating particles traveling at blasting velocities, conveyor means including spaced rotatable work hangers adapted to advance articles to be treated through said stream, said hangers being mutually spaced by distances at least several times as great as the width of said stream, means for driving said conveyor at a slow rate of speed during those portions of its travel in which the articles are passing through said stream, means for rotating said work hangers through a plurality of revolutions during the intervals in which the articles being advanced thereby are being treated in said stream, and means operated in timed relation to the movement of said conveyor for driving said conveyor at a relatively high rate of speed during intervals intervening between said treating intervals.

15. Apparatus for blast treating castings, forgings, and like articles, comprising means for establishing a stream of treating particles traveling at blasting velocities, conveyor means adapted to advance articles sequentially and in spaced relation through said stream to be treated thereby, differential driving means arranged to drive said conveyor at a slow rate of speed through those portions of its travel in which the articles are being treated in said stream and at a relatively high rate of speed during intervals intervening between said treating intervals, and means for adlusting the slow rate of speed imparted to said conveyor by said driving means.

16. Apparatus for blast treating castings, forgings, and like articles, comprising means for establishing a stream of treating particles traveling at blasting velocities, conveyor means adapted to advance articles sequentially and in spaced relation through said stream to be treated thereby, difierential driving means arranged to drive said conveyor at a, slow rate of speed through those portions of its travel in which the articles are being treated in said stream and at a relatively high rate of speed during intervals intervening between said treating intervals, means for adjusting the slow rate of speed imparted to said conveyor by said drive means, and means for adjusting the relative extent of slow and high speed travel imparted to said conveyor by said driving means.

1'7. Apparatus for blast treating castings, forgings, and like articles comprising means for establishing a stream of treating particles traveling at blasting velocities, conveyor means including spaced rotatable work hangers adapted to advance articles to be treated through said stream, said hangers being mutually spaced by distances at least several times as great as the width of said stream, means for driving said conveyor at a slow rate of speed during those portions of its travel in which the articles are passing through said stream, means for rotating said work hangers through a plurality of revolutions during the intervals in which the articles being advanced thereby are being treated in said stream, and means for adjusting the relative extent of slow and high speed travel imparted to said conveyor by said driving means.

18. Apparatus for blast treating castings, forgings, and like articles comprising blasting means establishing a stream of treating particles traveling at blasting velocities, conveyor means including spaced rotatable work supports adapted to advance articles sequentially through said stream to be treated thereby, means for rotatin said work supports as the articles are passing through said stream, means for continuously driving said conveyor alternately at low and high rates of speed, and means for predetermining the location of the work supports relative to said blasting means at the beginning and end of each period of low speed driving.

19. Apparatus for blast treating castings, forgings, and like articles comprising blasting means establishing a stream of treating particles traveling at blasting velocities, conveyor means including spaced rotatable work supports adapted to ad vance articles sequentially through said stream to be treated thereby, means for rotating said work supports as the articles are passing through said stream, means for continuously driving said conveyor alternately at low and high rates of speed,

means for adjusting the speed of low rate drive, and means for predetermining the location of the work supports relative to said blasting means at the beginning and end of each period of low speed driving.

20. Apparatus for blast treating castings, forgings, and like articles comprising blasting means establishing a stream of treating particles traveling at blasting velocities, conveyor means including spaced rotatable work supports adapted to advance articles sequentially through said stream to be treated thereby, means for rotating said work supports as the articles are passing through said stream, means for continuously driving said conveyor alternately at low and high rates of speed, means for predetermining the location of the work supports relative to said blasting means at the beginning and end of each period of low rate driving, and means for adjusting the rate at which the work supports are rotated during periods of slow speed driving of the conveyor.

21. In a method of blast treating articles of the type in which a series of articles are advanced sequentially in a path passing through a blasting zone, and in which blasting particles are continuously projected across the path traversed by said articles at said blasting zone, the improvement which consists in rotating and slowly traversing each article as it is passing through said blasting zone, and rapidly traversing the sequentially advancing articles during intervals between presentation of the successive articles to said blasting zone.

22. Apparatus for blast-treating castings, forgings and like articles, comprising means for establishing a stream of treating particles traveling at blasting velocities, conveyor means arranged to advance articles sequentially and in spaced relation through said stream to be treated thereby, and differential driving means arranged to drive said conveyor at a slow rate of speed during those portions of its travel in which the articles are being treated in said stream and at a relatively high rate of speed during the remaining portions of its travel, said diiierential driving means comprising a continuously operating slow speed drive motor, a driving connection between said motor and said conveyor, an overriding clutch in said driving connection, a high speed drive motor connected in driving relation to said conveyor and means for intermittently connecting said high speed motor to drive said conveyor except during the portions of its 1/ travel in which the articles are being treated in said stream.

23. A method of blast-treating castings, forgings and like articles being translated along a path leading to, through and away from a blasting zone having a blast stream directed across the path thereat, which consists in moving the article to be treated continuously along said path at a rapid rate until its leading edge is located in the blasting zone, then continuing to move the article along said path but at a slower rate until its trailing edge only is in said blasting zone, then continuing to move said article along said path at a rapid rate to remove it from the blasting zone, and rotating the article during its interval of slow travel through the blasting zone so as to expose all sides of it substantially equally to the blast stream.

24. A method of blast-treating castings, forgings, and like articles being translated along a path leading through a, plurality of blast streams widely spaced longitudinally therealong and each directed thereacross, which consists in moving the article to be treated continuously along said path at a rapid rate while not in said blast streams and at a slow rate while being treated therein, and rotating the article during its exposure to said blast streams so as to expose all sides of it substantially equally to the blast streams.

25. A method of blast-treating castings, iorg- 16 ings. and like articles being translated along a path leading through a plurality of blast streams widely spaced longitudinally therealong and each directed thereacross, which consists in continuously moving a series of articles to be treated along said path in spaced relation corresponding to the spacing of said blast streams, effecting said continuous movement at a slow rate while articles are being treated in said blast streams and at a rapid rate in the intervals during which the articles are moving from one blast stream to the next, and rotating the articles during their exposure to said blast streams so as to expose all sides of them substantially equally to the blast streams.

ROBERT B. HUYETT.

REFERENCES CITED The 'following references are of record in the flle of this patent:

UNITED STATES PATENTS Number Name Date 1,363,395 Crook Dec. 28, 1920 1,508,825 Sundstrand Sept. 16 ,1924 2,060,437 Harley Nov. 10, 1936 2,239,714 Hammell Apr. 29, 1941 2,344,476 Turnbull Mar. 14, 1944 2,368,061 Wortendyke Jan. 23, 1945 

